Self emulsifying drug delivery systems for poorly soluble drugs

ABSTRACT

A pharmaceutical composition in a form of a self-microemulsifying drug delivery system comprising: one or more therapeutic agent(s) which have low solubility in water or are water-insoluble, vitamin E, one co-solvent selected from propylene glycol and ethanol, one or more bile salts, TPGS, and one further surfactant selected from Tyloxapol and polyoxyl hydrogenated castor oil.

The present invention relates to a pharmaceutical excipient formulation,more particularly to a pharmaceutical pre-emulsion excipient enhancingthe absorption of poorly water soluble drugs, particularly the oralabsorption of taxoids.

The clinical use of some drugs is possible only if a drug deliverysystem is developed to transport them to their therapeutic target in thehuman body. This problem is particularly critical for water insoluble orpoorly water soluble compounds for which direct injections may beimpossible.

A few examples of therapeutic substances, which are poorly hydrosoluble,are the following: Palmitoyl Rhizoxin, Penclomedine, Vitamin A and itsderivatives (retinoic acid, isotretinoin, etc.), Tamoxifen, Etoposide,Campothecin, Navelbine, Valproic acid, Tacrolimus, Sirolimus(Rapanycin), Cyclosporin A, Clarithromicin, Testosterone, Estradiol,Progesterone, Ciprofloxacine, Fenofibrate, Benzafibrate, Azithromicine,Itraconazole, Miconazole, Propofol, Brimonidine, Latanoprost, andPaclitaxel.

Paclitaxel, one of the best known taxoid, disrupts tubulin dynamics. Ithas a significant clinical activity against a broad range of tumor typesincluding breast, lung, head and neck, bladder, and platinum-refractoryovarian carcinoma (E. K. Rowinsky. The development and clinical utilityof the taxoid class of antimicrotubule chemotherapy agents. Annu RevMed. 48: 353-74 (1997)). However, paclitaxel has a low therapeuticindex. It is a complex diterpenoid product, with a bulky, extended fusedring system as well as a number of hydrophobic substituents, which leadto its poor solubility in water (1 μg/ml) resulting in seriousformulation problems (R. T. Liggins, W. L. Hunter, H. M. Burt.Solid-state characterization of paclitaxel. J Pharm Sci. 86: 1458-63(1997)). It is highly lyophobic and the solubility of paclitaxel inlipophilic solvents, such as soybean oil is quite low and precludes theuse of simple oil-in-water emulsions for formulation considerations. Thecommercially available product, Taxol®, is currently formulated forsystemic administration in a mixture of ethanol and polyoxyethylatedcastor oil; the latter appears to be primarily responsible for drugrelated hypersensitivity reactions, rather than the drug itself (R. E.Gregory, A. F. De Lisa. Paclitaxel: a new antineoplastic agent forrefractory ovarian cancer. Clin Pharm. 12: 401-15 (1993)). Moreover,polyoxyethylated castor oil also causes the nonlinear pharmacokineticbehavior of paclitaxel (A. Sparreboom, O. van Tellingen, W. J. Nooijen,J. H. Beijnen. Nonlinear pharmacokinetics of paclitaxel in mice resultsfrom the pharmaceutical vehicle Cremophor EL. Cancer Res. 56: 2112-5(1996); O. van Tellingen, M. T. Huizing, V. R. Panday, J. H. Schellens,W. J. Nooijen, J. H. Beijnen. Cremophor EL causes (pseudo-) non-linearpharmacokinetics of paclitaxel in patients. Br J Cancer 81: 330-5(1999)).

The current approaches for reducing the side effects of the actualcommercial product are mainly focused on developing formulations thatare devoid of polyoxyethylated castor oil. Several attempts have beenmade to deliver paclitaxel using alternative systems, such asnanoparticles (R. Cavalli, O. Caputo, M. R. Gasco. Preparation andcharacterization of solid lipid nanospheres containing paclitaxel. Eur JPharm Sci. 10: 305-9 (2000); S. S. Feng, G. F. Huang, L. Mu. Nanospheresof biodegradable polymers: a system for clinical administration of ananticancer drug paclitaxel (Taxol). [In Process Citation]. Ann Acad MedSingapore. 29: 633-9 (2000)), liposomes (P. Crosasso, M. Ceruti, P.Brusa, S. Arpicco, F. Dosio, L. Cattel. Preparation, characterizationand properties of sterically stabilized paclitaxel-containing liposomes.J Controlled Release. 63: 19-30 (2000); A. Sharma, R. M. Straubinger.Novel taxol formulations: preparation and characterization oftaxol-containing liposomes. Pharm Res. 11: 889-96 (1994)), water-solubleprodrugs (J. M. Terwogt, B. Nuijen, W. W. T. B. Huinink, J. H. Beijnen.Alternative formulations of paclitaxel. Cancer Treat Rev. 23: 87-95(1997); A. Pendri, C. D. Conover, R. B. Greenwald. Antitumor activity ofpaclitaxel-2′-glycinate conjugated to poly(ethylene glycol): awater-soluble prodrug. Anticancer Drug Des. 13: 387-95 (1998)),emulsions (P. P. Constantinides, K. J. Lambert, A. K. Tustian, B.Schneider, S. Lalji, W. Ma, B. Wentzel, D. Kessler, D. Worah, and S. C.Quay. Formulation development and antitumor activity of afilter-sterilizable emulsion of paclitaxel. Pharm Res. 17: 175-82(2000); B. B. Lundberg. A submicron lipid emulsion coated withamphipathic polyethylene glycol for parenteral administration ofpaclitaxel (Taxol). J Pharm Pharmacol. 49: 16-21 (1997); P. Kan, Z. B.Chen, C. J. Lee, I. M. Chu. Development of nonionicsurfactant/phospholipid o/w emulsion as a paclitaxel delivery system. JControlled Release. 58: 271-8 (1999), P. Simamora, R. M. Dannenfelser,S. E. Tabibi, S. H. Yalkowsky. Emulsion formulations for intravenousadministration of paclitaxel. PDA J Pharm Sci Technol. 52: 170-2 (1998))and microspheres (R. T. Liggins, S. D'Amours, J. S. Demetrick, L. S.Machan, H. M. Burt. Paclitaxel loaded poly(L-lactic acid) microspheresfor the prevention of intraperitoneal carcinomatosis after a surgicalrepair and tumor cell spill [In Process Citation]. Biomaterials. 21:1959-69 (2000); Y. M. Wang, H. Sato, I. Adachi, I. Horikoshi.Preparation and characterization of poly(lactic-co-glycolic acid)microspheres for targeted delivery of a novel anticancer agent, taxol.Chem Pharm Bull (Tokyo). 44: 1935-40 (1996)). However, the success isfor the moment still limited. None of these alternatives has reached thestage of replacing polyoxyethylated castor oil based vehicle in theclinical application.

Another approach to overcome the hypersensitivity reactions resultingfrom polyoxyethylated castor oil can be the design of oral formulationsof paclitaxel, even in the presence of polyoxyethylated castor oil,since it is not orally absorbed (J. M. M. Terwogt, M. M. Malingre, J. H.Beijnen, W. W. B. Huinink, H. Rosing, F. J. Koopman, O. van Tellingen,M. Swart, and J. H. M. Schellens. Coadministration of oral cyclosporin Aenables oral therapy with paclitaxel. Clin Cancer Res. 5: 3379-84(1999)). Oral administration of paclitaxel would, thus, prevent theadverse effects caused by the vehicle substance polyoxyethylated castoroil and offer additional advantages over i.v. administration, includingelimination of the need for frequent visits to the outpatient clinic andeasier chronic administration (R. T. Dorr. Pharmacology and toxicologyof Cremophor EL diluent. Ann Pharmacother. 28: S11-4 (1994)). However,preclinical studies have suggested that paclitaxel is not significantlyabsorbed after oral administration; the systemic bioavailability inhumans after oral paclitaxel administration is less than 6% (J. M. M.Terwogt, M. M. Malingre, J. H. Beijnen, W. W. B. Huinink, H. Rosing, F.J. Koopman, O. van Tellingen, M. Swart, and J. H. M. Schellens.Coadministration of oral cyclosporin A enables oral therapy withpaclitaxel. Clin Cancer Res. 5: 3379-84 (1999)). The explanationsproposed to account for the poor oral bioavailability of paclitaxel aremultifactorial. The most likely explanations are its affinity for themembrane-bound drug efflux pump P-glycoprotein (P-gp), metabolization bycytochrome P450 and poor water solubility (R. T. Liggins, W. L. Hunter,H. M. Burt. Solid-state characterization of paclitaxel. J Pharm Sci. 86:1458-63 (1997); J. van Asperen, O. van Tellingen, A. Sparreboom, A. H.Schinkel, P. Borst, W. J. Nooijen, and J. H. Beijnen. Enhanced oralbioavailability of paclitaxel in mice treated with the P-glycoproteinblocker SDZ PSC 833. Br J Cancer. 76: 1181-3 (1997); C. D. Britten, S.D. Baker, L. J. Denis, T. Johnson, R. Drengler, L. L. Siu, K. Duchin, J.Kuhn, and E. K. Rowinsky. Oral paclitaxel and concurrent cyclosporin A:targeting clinically relevant systemic exposure to paclitaxel. ClinCancer Res. 6: 3459-68 (2000)). A number of studies have been carriedout to verify in both animals and patients if the oral bioavailabilityof paclitaxel can be greatly improved when the drug is administered withP-gp inhibitors (R. T. Dorr. Pharmacology and toxicology of Cremophor ELdiluent. Ann Pharmacother. 28: S11-4 (1994); J. van Asperen, O. vanTellingen, A. Sparreboom, A. H. Schinkel, P. Borst, W. J. Nooijen, andJ. H. Beijnen. Enhanced oral bioavailability of paclitaxel in micetreated with the P-glycoprotein blocker SDZ PSC 833. Br J Cancer. 76:1181-3 (1997); C. D. Britten, S. D. Baker, L. J. Denis, T. Johnson, R.Drengler, L. L. Siu, K. Duchin, J. Kuhln, and E. K. Rowinsky. Oralpaclitaxel and concurrent cyclosporin A: targeting clinically relevantsystemic exposure to paclitaxel. Clin Cancer Res. 6: 3459-68 (2000)).Cyclosporine A (CsA), a well-known immunosuppressive agent, was shown tobe one of the most promising P-gp inhibitors to enhance the oralabsorption of paclitaxel (J. M. M. Terwogt, M. M. Malingre, J. H.Beijnen, W. W. B. Huinink, H. Rosing, F. J. Koopman, O. van Tellingen,M. Swart, and J. H. M. Schellens. Coadministration of oral cyclosporin Aenables oral therapy with paclitaxel. Clin Cancer Res. 5: 3379-84(1999); C. D. Britten, S. D. Baker, L. J. Denis, T. Johnson, R.Drengler, L. L. Siu, K. Duchin, J. Kuhn, and E. K. Rowinsky. Oralpaclitaxel and concurrent cyclosporin A: targeting clinically relevantsystemic exposure to paclitaxel. Clin Cancer Res. 6: 3459-68 (2000)).CsA is a registered drug and thus is more readily available for clinicalstudies. However, the use of CsA for long-term oral dosing may behindered by its immunosuppressive side effect, which renders thiscompound less suitable for chronic use in cancer patients most of whomare already immunodeficient because of chemotherapy.

Recently, it was reported that self-emulsifying drug delivery systems(SEDDS) consisting of isotropic mixtures of oil and surfactants couldsignificantly improve the oral availability of poorly absorbed,hydrophobic and/or lipophilic drugs (T. Gershanik, S. Benita.Self-dispersing lipid formulations for improving oral absorption oflipophilic drugs. Eur J Pharm Biopharm. 50: 179-88 (2000)). SEDDS arecomposed of natural or synthetic oils, surfactants and one or morehydrophilic solvents and co-solvents. The principal characteristic ofSEDDS is their ability to form fine oil-in-water emulsions ormicroemulsions upon mild agitation following dilution by aqueous phases.These formulations can disperse in the gastrointestinal lumen to formmicroemulsions or fine emulsions, upon dilution with gastrointestinalfluids. In in-vivo absorption studies in non-fasting dogs, SEDDSelicited at least a three-fold greater C_(max) and AUC of a lipophilicnaphthalene derivative than that of the drug in any other dosage form(N. H. Shah, M. T. Carvajal, C. I. Patel, M. H. Infeld, A. W. Malick.Self-emulsifying drug delivery systems (SEDDS) with polyglycolyzedglycerides for improving in vitro dissolution and oral absorption oflipophilic drugs. Int J Pharm. 106: 15-23 (1994)). The absorption ofontazolast in rats was significantly enhanced by all lipid-basedformulations (D. J. Hauss, S. E. Fogal, J. V. Ficorilli, C. A. Price, T.Roy, A. A. Jayaraj, and J. J. Kierns. Lipid-based delivery systems forimproving the bioavailability and lymphatic transport of a poorlywater-soluble LTB4 inhibitor. J Pharm Sci. 87: 164-9 (1998)).Microemulsions have successfully been used to improve drugsolubilization/dissolution and/or intestinal absorption of poorlyabsorbed drugs including CsA pr(P. P. Constantinides. Lipidmicroemulsions for improving drug dissolution and oral absorption:physical and biopharmaceutical aspects. Pharm Res. 12: 1561-72 (1995);S. Tenjarla. Microemulsions: an overview and pharmaceuticalapplications. Crit Rev Ther Drug Carrier Syst. 16: 461-521 (1999)).

The objective of the present invention is to provide a pharmaceuticalcomposition in the form of a self micro-emulsifying drug delivery systemcomprising bile salts, for example sodium deoxycholate.

The invention is directed to a pharmaceutical composition comprising:

-   -   one or more therapeutic agent(s) which have low solubility in        water or are water-insoluble,    -   vitamin E,    -   one co-solvent selected from propylene glycol and ethanol,    -   one or more bile salts, for example sodium deoxycholate,    -   TPGS, and    -   one further surfactant selected from Tyloxapol and polyoxyl        hydrogenated castor oil.

In an advantageous embodiment, the bile salt is sodium deoxycholate.

In another advantageous embodiment, the one or more bile salts represent1 to 40% (w/w) of the final composition. For example, the sodiumdeoxycholate represents 1 to 40% (w/w) of the final composition;

In another advantageous embodiment, the vitamin E is from 2 to 6% (w/w)of the final composition.

According to the present invention, therapeutic agents are any compoundwhich has a biological activity and is soluble in the oil phase. Saidtherapeutic agents may be antibiotics, analgesics, antidepressants,antipsychotics, hormones or chemotherapeutics.

Agents like taxoids, i.e. paclitaxel, docetaxel, their derivatives,analogs and prodrugs are preferred.

Preferred compositions according to the invention contain a relativeproportion of paclitaxel between 0.5 and 4% (w/w), preferably equal to3% (w/w).

Preferred pharmaceutical composition according to the instant inventioncomprises an emulsion including vitamin E, D-α-tocopheryl polyethyleneglycol succinate 1000 (TPGS), polyoxyl hydrogenated castor oil and atleast, one therapeutic agent, the relative proportions of vitamin E,TPGS and polyoxyl hydrogenated castor oil being respectively 10-60,40-90, 10-80 (w/w) of the total oil phase, more preferably 10-45, 10-65and 10-60.

Another preferred pharmaceutical composition according to the inventioncontains a relative proportion of vitamin E, TPGS, sodium deoxycholateand Tyloxapol are respectively 2-6, 5-60, 1-40 and 5-70 (w/w) of thetotal oil phase.

More preferably, the relative proportions of vitamin E, TPGS, sodiumdeoxycholate and Tyloxapol are respectively 3-5, 20-35, 2-20 and 20-40%(w/w) of the total oil phase.

Concerning co-solvent, the relative proportions of propylene glycol arein the range of 0-50% (w/w) of the final formulation, preferably equalto 20% (w/w) and the relative proportions of ethanol are in the range of5-50% (w/w) of the final formulation, preferably equal to 30% (w/w).

The composition according to the invention may be associated with anypharmaceutical excipient to form a dosage form, which can beadministered to animals or humans via intravascular, oral,intramuscular, cutaneous and subcutaneous routes. Specifically emulsionsaccording to the invention can be given by any of the following routesamong others: intra-abdominal, intra-arterial, intra-articular,intra-capsular, intra-cervical, intra-cranial, intra-ductal,intra-dural, intra-lesional, intra-ocular, intra-locular, intra-lumbar,intra-mural, intra-operative, intra-parietal, intra-peritoneal,intra-plural, intra-pulmonary, intra-spinal, intra-thoracic,intra-tracheal, intra-tympanic, intra-uterine, intra-ventricular ortransdermal or can be nebulised using suitable aerosol propellants.

The microemulsifying compositions according to the instant invention maybe used for the treatment of different diseases like cancers, tumours,Kaposi's sarcoma, malignancies, uncontrolled tissue or cellularproliferation secondary to tissue injury, and any other diseaseconditions responsive to toxoids such as paclitaxel and docetaxel,and/or prodrugs and derivatives of the foregoing. Among the types ofcarcinoma which may be treated particularly effectively with oralpaclitaxel, docetaxel, other taxoids, and their prodrugs andderivatives, are hepatocellular carcinoma and liver metastases, cancersof the gastrointestinal tract, pancreas, prostate and lung, and Kaposi'ssarcoma. Examples of non-cancerous disease conditions which may beeffectively treated with these active agents administered orally inaccordance with the present invention are uncontrolled tissue orcellular proliferation secondary to tissue injury, polycystic kidneydisease, inflammatory diseases (e.g., arthritis) and malaria.

The novel compositions may be administered in any known pharmaceuticaloral dosage form. For example, the formulations may be encapsulated in asoft or hard gelatin capsule or may be administered in the form of aliquid oily preparation. Each dosage form may include, apart from theessential components of the composition conventional pharmaceuticalexcipients, diluents, sweeteners, flavouring agents, colouring agentsand any other inert ingredients regularly included in dosage formsintended for oral administration (see e.g., Remington's PharmaceuticalSciences, 17th Ed., 1985).

Precise amounts of each of the target drugs included in the oral dosageforms will vary depending on the age, weight, disease and condition ofthe patient.

Although some of the oral formulations of the invention may providetherapeutic blood levels of the taxoid active ingredient whenadministered alone, an advantageous method of the invention for treatingmammalian patients (particularly human patients) suffering fromtaxoid-responsive disease conditions is to administer the oralformulations containing the taxoid target agent concomitantly with theadministration of at least one dose of an oral bioavailability enhancingagent. An other advantageous method of the invention for treatingmammalian patients is to administer the oral formulations containing thetaxoid target agent concomitantly or separately with another antitumoragent like carboplatinum and the like.

The preferred embodiment of the method of the invention for oraladministration to humans of paclitaxel, its derivatives, analogs andprodrugs, and other taxoids comprises the oral administration of an oralabsorption or bioavailability enhancing agent to a human patientsimultaneously with, or prior to, or both simultaneously with and priorto the oral administration to increase the quantity of absorption; ofthe intact target agent into the bloodstream.

Different advantages of the present invention will be readilyappreciated with the following tables, drawings and examples.

FIG. 1 a illustrates the pseudo-ternary diagram of SEDDS containing1.25% paclitaxel, 10% DOC-Na, and 20% propylene glycol following 1:10dilution with water.

A: microemulsions and/or micellar solutions stable for at least 6 hourswith no paclitaxel precipitation.

B: microemulsions and/or micellar solutions, but, paclitaxelprecipitation within 6 hours.

C: emulsions or opaque dispersions with droplet size larger than 100 nm,whereas, no paclitaxel precipitation noted within 6 hours.

FIG. 1 b illustrates the pseudo-ternary diagram of SEDDS containing 5%vitamin E, 30% ethanol and 3% paclitaxel following 1:10 dilution withwater.

A: microemulsions and/or micellar solutions stable for at least 2 hourswith no paclitaxel precipitation, with droplet size in the range 1 to 10nm.

B: submicron emulsions stable for at least 2 hours with no paclitaxelprecipitation, with droplet size in the range of 40 to 400 nm.

FIG. 2 illustrates the drug logarithmic concentration-time profilesafter intravenous administration of Taxol® and paclitaxel SEDDS: (a) 2,(b) 5 and (c) 10 mg/kg paclitaxel. Data are expressed as means±S.D.(n=3).

FIG. 3 illustrates the plasma paclitaxel concentration-time profilesafter oral administration at the doses of (A) 2, (B) 5 and (C) 10 mg/kgpaclitaxel, and (D) 2 mg/kg paclitaxel of SEDDS with 40 mg/kg CsA. Dataare expressed as means±S.D. (n=3).

FIG. 4 illustrates the relationship between dose-adjusted AUC andadministered dose for: (A) intravenous and (B) oral administration.

FIG. 5 illustrates the plasma paclitaxel concentration-time profilesafter oral administration at constant drug concentration in the SEDDSadministered at different doses.

EXAMPLE 1 Characterization of Paclitaxel Emulsions Following 1:10Dilution with Water

1. Materials and Methods

1.1 Materials

Paclitaxel (MW 853) with 99.34% (w/w) purity (HPLC) was purchased fromFarmachem (Lugano, Switzerland). Vitamin E, deoxycholic acid sodium salt(DOC-Na) and Tyloxapol were bought from Sigma (St. Louis, Mo., USA).D-α-tocopheryl polyethylene glycol succinate 1000 (TPGS) was a gift fromEastman Chemical (Kingsport, Tenn., USA). Ethanol was bought from SDS(Peypin, France). All solvents were HPLC grade.

1.2 Methods

1.2.1. Preparation of Paclitaxel SEDDS with Polyoxyl Hydrogenated CastorOil

The blank formulation consisted of vitamin E, TPGS, polyoxylhydrogenated castor oil, DOC-Na and propylene glycol. Paclitaxel wasweighed and added to the blank formulation and thoroughly mixed to forma clear homogenous mixture. Paclitaxel emulsions may be formed following1:10 dilution of SEDDS with distilled water. A ternary phase diagramstudy (S. Watnasirichaikule, N. M. Davies, T. Rades, I. G. Tucker.Preparation of biodegradable insulin nanocapsules from biocompatiblemicroemulsions. Pharm Res. 17: 684-9 (2000); M. Trotta, E. Ugazio, M. R.Gasco. Pseudo-ternary phase diagrams of lecithin-based microemulsions:influence of monoalkylphosphates. J Pharm Pharmacol. 47: 451-4 (1995))was carried out to identify the optimal SEDDS containing paclitaxel atdifferent concentrations ranging from 0.5 to 2.5% (w/w). In thetriangular phase diagram study, vitamin E, TPGS and polyoxylhydrogenated castor oil concentrations were varied, while, the DOC-Naand propylene glycol concentrations remained constant at 10 and 20%(w/w), respectively, in all compositions. The values shown in thediagram for each excipient were always calculated in percentage from thetotal combination which, in fact, represented only 70% of the finalcomposition.

1.2.2. Preparation of Paclitaxel SEDDS with Tyloxapol

The vitamin E and TPGS are mixed and DOC-Na is added in one hand. In theother hand, Tyloxapol and ethanol are mixed and paclitaxel is dissolvedin said mixture. The drug containing Tyloxapol and ethanol mixture isadded to vitamin E-TPGS-DOC-Na mixture to form a clear homogeneous oilymixture. Paclitaxel emulsion may be formed by dilution of SEDDS withdistilled water.

Ternary phase diagram study was carried out as disclosed before. In thepseudo-ternary phase diagram study, DOC-Na, TPGS and Tyloxapolconcentration were varied while the ethanol, vitamin E and paclitaxelconcentrations remain constant in all compositions. The values shown inthe diagram for each excipient were always calculated in percentagesfrom the combination of the three excipients. This combinationrepresents 62% of the final composition while ethanol, vitamin E andpaclitaxel represent 38%.

Droplet Size

Emulsions were formed following 1:10 dilution of paclitaxel SEDDS withdistilled water. The droplet size of the resultant emulsions wasdetermined by the PCS method using a Coulter® Model N₄SD (FL, USA).

Zeta Potential

The Zeta potential of the resultant emulsions after 1:10 dilution ofSEDDS with water was measured by a Malvern Zetasizer 3000 (Malvern, UK).

Stability Study

Optimal SEDDS formulations obtained in 1.2.1. containing 0.5, 1.0, 1.5,2.0, 2.5 and 3% (w/w) paclitaxel were prepared. Microemulsions wereformed after 1:10 dilution with pre-warmed distilled water (37° C.) andthen stored at 37° C. to monitor the possible precipitation ofpaclitaxel. The chemical stability of paclitaxel in SEDDS containing0.5-3% w/w paclitaxel at 4 and 25° C. was monitored using an analyticalHPLC method (M. Andreeva, P. D. Iedmann, L. Binder, V. W. Armstrong, H.Meden, M. Binder, M. Oellerich. A simple and reliable reversed-phasehigh-performance liquid chromatographic procedure for determination ofpaclitaxel (taxol) in human serum. Ther Drug Monit. 19: 327-32 (1997);A. Sharma, W. D. Conway, R. M. Straubinger. Reversed-phasehigh-performance liquid chromatographic determination of taxol in mouseplasma. J Chromatogr B Biomed Appl. 655: 315-9 (1994)).

2. Results

2.1 SEDDS Preparation

2.1.a SEDDS with Polyoxyl Hydrogenated Castor Oil

FIG. 1 a shows that the formulations containing 1.25% paclitaxel, 10%DOC-Na and 20% propylene glycol in shaded area A of the ternary diagramcan form microemulsions and/or micellar solutions following 1:10dilution with water. The resultant microemulsions or micellar solutionscan remain physically stable for at least 6 hours with no paclitaxelprecipitation. The combination of vitamin E (28.5% w/w), TPGS (43.0%w/w) and polyoxyl hydrogenated castor oil (28.5% w/w), located at thecenter of area A, was chosen as the optimal formulation. Thecorresponding optimal blank formulation, therefore, consisted of (%,w/w) vitamin E (20), TPGS (30), polyoxyl hydrogenated castor oil (20),DOC-Na (10) and propylene glycol (20).

The formulations located in area B following aqueous dilution (1:10) doform microemulsions or micellar solutions, but paclitaxel precipitationappeared within 6 hours.

The formulations located at area C can form emulsions or opaquedispersions with main droplet size larger than 100 nm whereas nopaclitaxel precipitate was noted within 6 hours.

Vitamin E used in paclitaxel SEDDS forms the oil phase in the resultantmicroemulsions after dilution of SEDDS with an aqueous phase. Vitamin Emay not only improve the incorporation of paclitaxel into SEDDS to formstable microemulsions, but also might produce beneficial protectiveeffects by quenching free radicals (K. Kline, W. Yu, B. G. Sanders.Vitamin E: mechanisms of action as tumor cell growth inhibitors. J Nutr.131: 161S-163S (2001)). Furthermore, TPGS, a water-soluble surfactant,inhibits the P-gp efflux system, and thus, have a beneficial effect inimproving the oral absorption of paclitaxel (R. J. Sokol, et al.Improvement of cyclosporin absorption in children after livertransplantation by means of water-soluble vitamin E. Lancet. 338: 212-4(1991) and J. M. Dintaman, J. A. Silverman. Inhibition of P-glycoproteinby D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS). PharmRes. 16: 1550-6 (1999)).

2.1.b. SEEDS with Tyloxapol

FIG. 1 b shows that the formulations containing 3% paclitaxel, 5%vitamin E and 30% ethanol in grey area A of the ternary diagram can formmicroemulsions and/or micellar solutions following 1:10 dilution withwater. The resultant microemulsions or micellar solutions, with dropletsize in the range of 1 to 10 nm, can remain physically stable for atleast 2 hours with no paclitaxel precipitation. The combinations of TPGS(20-35% w/w), sodium deoxycholate (2-20% w/w) and Tyloxapol (20-40%w/w), located near the center of area A, were chosen as the optimalformulations.

The formulations located in dark grey area B of the ternary diagramfollowing aqueous dilution (1:10) do form submicron emulsions withdroplet size in the range of 40 to 400 nm, with no paclitaxelprecipitation for at least 2 hours.

2.2 Physicochemical Characterization

2.2.a. SEDDS with Polyoxyl Hydrogenated Castor Oil

Following 1:10 dilution of paclitaxel SEDDS (1.25% w/w) in distilledwater, the droplet size of the resultant microemulsions was 31.5±4.0 nmfor unimodal results and 1.0±0.4 nm for SDP weight results. Theresultant microemulsions were negatively charged, and the zeta potentialvalue was −45.5±0.5 mV.

2.2.b. SEEDS with Tyloxapol

Following 1:10 dilution of paclitaxel SEDDS in distilled water (3% w/w),the droplet size of the resultant microemulsions was 0.95±0.09 nm.

2.3 Stability Study

Following 1:10 dilution of optimal SEDDS containing variousconcentrations of paclitaxel, the precipitation of the drug from theresultant microemulsions depended on the initial concentration ofpaclitaxel in SEDDS. The physical stability of paclitaxel innicroemulsions decreased with the increase of paclitaxel concentrationin SEDDS formulations. When paclitaxel concentrations were lower than1.25% w/w, the precipitation time was longer than 6 h. No precipitatewas noted when the concentration was 0.5% w/w over 6 months. Whenpaclitaxel concentration was higher than 1.5% w/w, the drug precipitatedeasily from the resultant microemulsions. The precipitation time wasabout 2 h as the concentration was elevated to 2.5% w/w.

The preliminary chemical stability studies indicated that paclitaxel inthe negatively charged SEDDS was stable at 4 and 25° C. The drug contentin SEDDS at 4 and 25° C. did not change over three months.

EXAMPLE 2 Pharmacokinetics of Paclitaxel SEDDS

1. Materials and Methods

1.1 Animal Study

Experiments were performed on male Sprague-Dawley (S.D.) rats weighing200-250 g, which fasted overnight for 12-14 hours with free access towater. Experimental procedures were approved by the Hebrew University ofJerusalem Committee on Use and Care of Animals. Following 1:10 dilutionof SEDDS containing 0.5, 1.25 or 2.5% paclitaxel with water (oral) orsaline (intravenous), the microemulsions were orally or intravenouslyadministered at doses of 2.0, 5.0 or 10.0 mg/kg paclitaxel,respectively. In studies where indicated, CsA (40 mg/kg, Neoral®;Novartis, Basel, Switzerland) was orally administered 10 min before oraladministration of paclitaxel SEDDS. Blood samples were collected intoheparinized tubes at time points of 0.5, 1, 2, 4, 6, 8, 12 and 24 hoursafter oral dosing. Additional samples were collected at 1, 5, 15 min,1.5 h and 3 h post intravenous dosing. At each time point, three ratswere sacrificed to take the blood. All blood samples were immediatelyplaced on ice upon collection and centrifuged at 4000 rpm for 15 min toobtain the plasma. Aliquots were stored at −20° C. until analysis.

1.2 Analysis of Paclitaxel

Prior to extraction, 0.05-2.0 ml of rat plasma that was diluted to atotal of 2.0 ml with double distilled water for intravenousadministration or 2.0 ml plasma for oral administration was mixed with0.3 μg Taxotere®, dissolved in 50 μl methanol, used as an internalstandard. Extraction of paclitaxel was accomplished by adding 4.0 ml oftert-butyl methyl ether and vortex-mixing the sample for 1.0 min. Themixture was then centrifuged for 10 min at 4000 rpm, after which 3.0 mlof the organic layer was transferred to a clean tube and evaporated todryness under vacuum using a Labconco Vortex Evaporator (LumitronElectronic Instrument Ltd., MO, USA) at 200C. Approximately 200 μlmobile phase was used to reconstitute the residue and 80 μl aliquot wasinjected into the HPLC equipped with a Hypersil® BDS C₁₈ (5 μm, 250×4.6mm; Alltech, Deerfield, Ill., USA) analytical column and a Betasil C₁₈(5 μm, 10×4.6 mm; Alltech, Deerfield, Ill., USA) guard column. Thedetection wavelength of paclitaxel was 227 nm (M. Andreeva, P. D.Iedmann, L. Binder, V. W. Armstrong, H. Meden, M. Binder, M. Oellerich.A simple and reliable reverse-phase high-performance liquidchromatographic procedure for determination of paclitaxel (taxol) inhuman serum. Ther Drug Monit. 19: 327-32 (1997); A. Sharma, W. D.Conway, R. M. Straubinger. Reversed-phase high-performance liquidchromatographic determination of taxol in mouse plasma. J Chromatogr BBiomed Appl. 655: 315-9 (1994)). The mobile phase was acetonitrile-water(48:52) and pumped at the flow-rate of 1.5 ml/min. The analysis wascarried out at room temperature. The retention time of paclitaxel anddocetaxel was 12.4 and 11.0 min, respectively. The lower limit ofquantification for paclitaxel was 10 ng/ml, and the range of linearresponse was 50-800 ng/ml (r²>0.9990). The observed recovery ofpaclitaxel was 96.8-101.6%, and the intra-day and inter-day assayvariabilities were less than 5.6%.

1.3 Pharmacokinetic Data Analysis

Pharmacokinetic parameters in plasma were obtained from the pooledconcentration-time data of each experiment with statistical momentalgorithm using the WinNonlin program package. The AUC₀₋₂₄ from time 0to time 24 h (T₂₄) was calculated using the linear trapezoidal method,and AUC_(0-∞) was calculated by dividing the concentration of 24 h datapoint (C₂₄) by the elimination rate constant (k) as follows:AUC_(0-∞)=AUC₀₋₂₄+C₂₄/k.

The area under the first moment curve (AUMC) was calculated as follows:AUCM _(0-∞) =AUMC ₀₋₂₄+(T ₂₄ ·C ₂₄)/k+C ₂₄ /k

The relative bioavailability (Fr) and systemic (absolute)bioavailability (Fa) were calculated as follows:Fr=[(AUC _(SEDDS))_(oral)/(AUC _(Taxol))_(oral)]_(0-∞)Fa=[(AUC _(test))_(oral)/(AUC _(Taxol))_(i.v.)]₀₋₂₈

Thus, fr and fa, the relative and absolute bioavailability at 24 h,respectively, were calculated as follows:fr=[(AUC _(SEDDS))_(oral)/(AUC _(Taxol))_(oral)]₀₋₂₄fa=[(AUC _(test))_(oral)/(AUC _(Taxol))_(i.v.)]₀₋₂₄.

The mean residence time (MRT) was determined by dividing AUMC_(0-∞) byAUC_(0-∞).

2. Results

2.1 Intravenous Administration

Paclitaxel plasma concentration data obtained following the i.v.administration were analyzed by the non-compartment and two-compartmentmodels. FIGS. 2(A), (B) and (C) show the drug logarithmicconcentration-time profiles after i.v. administration of Taxol® andpaclitaxel SEDDS at the doses of 2, 5 and 10 mg/kg, respectively. Therelevant pharmacokinetic parameters are outlined in Table 1.

The clearance (Cl) of paclitaxel in Taxol® was 513.6, 433.8 and 118.3(ml/h·kg) at the doses of 2, 5 and 10 mg/kg, respectively. The clearanceof paclitaxel in SEDDS was 455.4, 493.6 and 137.3 (ml/h·kg) at the dosesof 2, 5 and 10 mg/kg, respectively. The AUC₀₋₂₈ of paclitaxel in Taxol®was 3894.4 (ng·h/ml) at the dose of 2 mg/kg, and it increased to 11525.5(ng·h/ml) at the dose of 5 mg/kg and 84517.5 (ng·h/ml) at the dose of 10mg/kg. The AUC₀₋₂₈ of paclitaxel in SEDDS was 4392.1 (ng·h/ml) at thedose of 2 mg/kg, and it escalated to 10129.9 (ng·h/ml) at the dose of 5mg/kg and 72846.3 (ng·h/ml) at the dose of 10 mg/kg. The maximumconcentration (C_(max)) and AUC_(0-∞) of paclitaxel increaseddisproportionately with higher doses, and the clearance of paclitaxeldecreased with the increase in dose, indicating a nonlinear or saturablepharmacokinetic behavior for Taxol® and SEDDS. The MRT and steady-statevolume of distribution (V_(ss)) decreased with the increase of the dose,but the MRT and V_(ss) of paclitaxel SEDDS were lower compared toTaxol®.

The absolute bioavailability of paclitaxel SEDDS was 112.1% at the doseof 2 mg/kg, and it decreased to 87.9% at the dose of 5 mg/kg and to86.2% at the dose of 10 mg/kg.

Taxol® showed serious toxicity problems in the present study, and about30% of the rats died at the dose of 10 mg/kg. On the contrary, therewere no side effects of paclitaxel SEDDS at the same dose.

2.2 Oral Administration

FIGS. 3(A), (B), and (C) show the plasma paclitaxel concentration-timeprofiles after oral administration at the doses of 2, 5 and 10 mg/kgpaclitaxel, respectively.

Paclitaxel plasma concentration-time profiles after oral administrationof 2 mg/kg paclitaxel SEDDS with 40 mg/kg CsA is shown in FIG. 3(D).Table 2 shows the relevant pharmacokinetic parameters calculated usingnon compartmental analysis.

Following 1:10 dilution of paclitaxel SEDDS with distilled water, theresultant microemulsions were orally administered to rats immediately.The values of C_(max) were between 40 and 60 ng/ml, except for thepaclitaxel SEDDS co-administered with CsA (160 ng/ml).

Compared with Taxol®, the AUC₀₋₂₄ of paclitaxel SEDDS increased slightlyat all indicated doses. The fr of paclitaxel SEDDS between 0 and 24 hincreased ranging from 1.5 to 10%, and this increase was inverselyproportional to the increase in dose (Table 2). The fa of paclitaxelSEDDS between 0 and 24 h was as high as 28.1% at the dose of 2 mg/kg,and then decreased to 8.3% at the dose of mg/kg and 1.1% at the dose of10 mg/kg. However, taken Taxol® as the standard formulation for theevaluation of bioavailability of paclitaxel SEDDS, the relativebioavailability (Fr) of paclitaxel SEDDS increased by 1.5% at the doseof 2 mg/kg, but it increased by 43.8% and 14.4% at the doses of 5 and 10mg/kg, respectively. The absolute bioavailability (Fa) was 42.7, 22.2and 1.0% at the doses of 2, 5 and mg/kg paclitaxel, respectively.

Compared to the fasted rats, the AUC of paclitaxel SEDDS in non-fastedrats at the dose of 5 mg/kg showed a little decrease, but it was higherthan that of Taxol®. This result indicated that there was a slightinfluence of foo'd intake on the absorption of paclitaxel. For the samedose (10 mg/kg paclitaxel) but different concentrations (0.5 and 2.5%w/w) of paclitaxel in SEDDS, the AUC of SEDDS with 0.5% w/w paclitaxelwas higher than that of SEDDS with 2.5% w/w paclitaxel (FIG. 3C). Thisindicated that the excipient concentration could slightly improve theabsorption of paclitaxel in SEDDS. When co-administered with CsA (40mg/kg), the AUC₀₋₂₄ of paclitaxel SEDDS increased 1.73 fold comparedwith that of Taxol® and 1.59 fold compared with that of SEDDS withoutCsA at the dose of 2 mg/kg paclitaxel. Moreover, the Cram significantlyincreased and reached the therapeutic level (0.1 μmol, equivalent to 85ng/ml). The duration of plasma concentration above 0.1 μmol lastednearly 4.0 h after oral paclitaxel SEDDS administration at the dose of 2mg/kg co-administered with 40 mg/kg CsA, but this threshold was notreached after oral administration of Taxol® or SEDDS alone following asingle dose administration. The relative bioavailability (Fr) ofpaclitaxel SEDDS with CsA was 133.9% and the absolute bioavailability(Fa) was 56.4% at the dose of 2 mg/kg. This indicates that CsA cangreatly increase the bioavailability of paclitaxel confirming previousreported results (J. M. M. Terwogt, M. M. Malingre, J. H. Beijnen, W. W.B. Huinink, H. Rosing, F. J. Koopman, O. van Tellingen, M. Swart, and J.H. M. Schellens. Coadministration of oral cyclosporin A enables oraltherapy with paclitaxel. Clin Cancer Res. 5: 3379-84 (1999); C. D.Britten, S. D. Baker, L. J. Denis, T. Johnson, R. Drengler, L. L. Siu,K. Duchin, J. Kuhn, and E. K. Rowinsky. Oral paclitaxel and concurrentcyclosporin A: targeting clinically relevant systemic exposure topaclitaxel. Clin Cancer Res. 6: 3459-68 (2000)).

The MRT₀₋₂₄ of paclitaxel SEDDS was similar to that of Taxol® at allindicated doses, except that of paclitaxel SEDDS co-administered withCsA. The MRT_(0-∞) of paclitaxel SEDDS increased at high doses comparedwith that of Taxol®. The MRT₀₋₂₄ and MRT_(0-∞) of paclitaxel SEDDSco-administered with CsA were the shortest among all oral formulationsat various doses.

As compared with Taxol®, the relative bioavailability of paclitaxelSEDDS increased by 43.8% at the dose of 5 mg/kg, and by 14.1 and 25.1%at the dose of 10 mg/kg for the SEDDS formulation containing 2.5 and0.5% w/w paclitaxel, respectively. For the same concentration ofexcipients in the formulation, the dose of 5 mg/kg paclitaxel hasachieved the highest bioavailability (Table 2), indicating that 1.25%w/w paclitaxel in SEDDS was the optimal concentration. Thedisproportionate decrease of mean C_(max) and AUC_(0-∞) (FIG. 4B) valueswith the increase of the dose suggested that there is a saturableprocess in the absorption of oral paclitaxel.

This study shows that paclitaxel microemulsions can form following 1:10dilution of SEDDS with an aqueous phase. The resulting microemulsionsbear a negative or a positive charge. The oral bioavailability ofpaclitaxel could be improved significantly when paclitaxel wasformulated into SEDDS.

An additional advantage of the SEDDS can be found in the convenience andcompliance of the patient. In order to administer an oral dose of 90mg/m² paclitaxel twice daily, 30 ml of the commercially available Taxol®would be required. This might bring with itself the possibility ofprecipitation of the drug and make the commercial viability of theproduct more difficult. However, such a problem would not be a concernwith the SEDDS used in the present study since the administered dose ofabout 180 mg, required for a 90 mg/m² dose, would be only 6-12 mldissolved in a glass of water, provided the concentration of the drugused is 2.5-1.25% w/w, respectively. And finally, the improved Fr and Favalues indicate that SEDDS is a promising system for improving the oralbioavailability of paclitaxel.

1. A pharmaceutical composition in a form of a self microemulsifyingdrug delivery system comprising: one or more therapeutic agent(s) whichhave low solubility in water or are water-insoluble, vitamin E, oneco-solvent selected from propylene glycol and ethanol, one or more bilesalts, TPGS, and one further surfactant selected from Tyloxapol andpolyoxyl hydrogenated castor oil.
 2. A pharmaceutical compositionaccording to claim 1, wherein the bile salt is sodium deoxycholate.
 3. Apharmaceutical composition according to claim 2, wherein the sodiumdeoxycholate represents 1 to 40% (w/w) of the final composition.
 4. Apharmaceutical composition according to claim 1, wherein vitamin E isfrom 2 to 6% (w/w) of the final composition.
 5. A pharmaceuticalcomposition according to claim 1, wherein the therapeutic agent is achemotherapeutic agent.
 6. A pharmaceutical composition according toclaim 5, wherein the chemotherapeutic agent is a taxoid.
 7. Apharmaceutical composition according to claim 6, wherein the taxoid isselected from paclitaxel, docetaxel, their derivatives, analogs andprodrugs.
 8. A pharmaceutical composition according to claim 7, whereinthe taxoid is paclitaxel.
 9. A pharmaceutical composition according toclaim 8, wherein the relative proportion of paclitaxel is between 0.5and 4% (w/w).
 10. A pharmaceutical composition according to claim 9,wherein the relative proportion of paclitaxel is 3% (w/w).
 11. Apharmaceutical composition according to claim 1 comprising at least onetherapeutic agent, wherein the relative proportions of vitamin E, TPGSand polyoxyl hydrogenated castor oil are respectively 10-60, 40-90 and10-80 (w/w) of the total oil phase.
 12. A pharmaceutical compositionaccording to claim 11 wherein the relative proportions of vitamin E,TPGS and polyoxyl hydrogenated castor oil are respectively 10-45, 10-65and 10-60 (w/w) of the total oil phase.
 13. A pharmaceutical compositionaccording to claim 1, wherein the relative proportions of vitamin E,TPGS, sodium deoxycholate and Tyloxapol are respectively 2-6, 5-60, 1-40and 5-70 (w/w) of the total oil phase.
 14. A pharmaceutical compositionaccording to claim 13, wherein the relative proportions of vitamin E,TPGS, sodium deoxycholate and Tyloxapol are respectively 3-5, 20-35,2-20 and 20-40 (w/w) of the total oil phase.
 15. A pharmaceuticalcomposition according to claim 1, wherein the relative proportions ofpropylene glycol are in the range of 0-50% (w/w) of the finalformulation, preferably equal to 20% (w/w) and the relative proportionsof ethanol are in the range of 5-50% (w/w) of the final formulation,preferably equal to 30% (w/w).
 16. A pharmaceutical dosage formcomprising a self emulsifying composition according to claim 1 andpharmaceutical excipients.
 17. A pharmaceutical dosage form according toclaim 16, which is suitable for the oral route.
 18. An oralpharmaceutical dosage form according to claim 17, wherein thecomposition is encapsulated in a soft or in a hard gelatin capsule. 19.An oral pharmaceutical dosage form according to claim 18, wherein thecomposition is a liquid oily preparation.
 20. Use of aself-microemulsifying composition according to claim 1 for themanufacture of a medicament useful in the treatment of taxoid-responsivediseases.
 21. Use according to claim 20 for administration to patientsreceiving simultaneously with, or prior to, bioavailability enhancingagent and/or another antitumor agent.